Process for preparing low fat potato chips and shoestring potatoes

ABSTRACT

A process for preparing potato chips, shoestring potatoes and other tuber chips in which no additional fat content is added to the potato and none of the natural foodstuffs are removed. The process comprises the steps of slicing a potato or other tuber to produce a plurality of slices or strips of the desired configuration, heating the slices or strips to a temperature and for a period of time sufficient to remove from about fifty to eighty percent of the moisture therefrom, and microwave heating the slices or strips to produce a product having substantially the same flavor, color, crispness and slightly greasy appearance as deep-fried products. The slices or strips can be subjected to a second microwaving step at a reduced power level to reduce the moisture content of the product for a longer shelf life.

This application is a continuation-in-part of applicant's application,Ser. No. 08/154,253, filed Nov. 18, 1993, now U.S. Pat. No. 5,393,543,which is a continuation-in-part of Ser. No. 08/030,794, filed Mar. 12,1993, now U.S. Pat. No. 5,292,540, which is a continuation-in-part ofSer. No. 07/712,943, filed Jun. 10,1991, now U.S. Pat. No. 5,194,277.

BACKGROUND OF THE INVENTION

The present invention relates to a process for producing potato chipsand shoestring potatoes, which have substantially the same flavor, colorand crispness as well as a slightly greasy appearance similar toconventional deep-fried products but in which no fat content is added tothe potato and no foodstuff is removed. Potato chips and shoestringpotatoes are typically produced by deep frying thin slices or strips ofraw potatoes in an oil. The deep frying process reduces the watercontent in the potatoes while adding oil to the product to produce thedesired color and crispness. However, the resulting product containsconsiderable oil, and thus fat, which is generally unhealthy.

With increased public awareness of the benefits of low fat foods,efforts have been undertaken to develop alternate methods for producingthe ever popular potato chip. Examples of such efforts are seen in U.S.Pat. Nos. 4,277,510, 4,283,425, 4,749,579 and 4,906,483. While reducingthe fat content of the resulting chip in comparison to the conventionaldeep frying process, the processes described in U.S. Pat. Nos. 4,277,510and 4,749,579 continue to employ the step of frying the slices of potatoin an oil and thus continue to add fat to the chip. The processdescribed in U.S. Pat. No. 4,906,483 like the present invention, employsmicrowave heating in lieu of deep frying, but additionally teaches theremoval of the starch from the potato chip and thus does not provide thewhole food content of the potato. The process described in U.S. Pat. No.4,283,425 also employs microwave cooking in lieu of frying to avoid theaddition of fat to the chip but teaches the necessity of coating thechip prior to the microwave heating thereof with a globular protein suchas soy isolate or egg albumen. As certain individuals are allergic tosoy and dairy products and others prefer natural foods with noadditives, such a process would be somewhat limited in its appeal. Incontrast to the above processes, the process of the present inventionnot only provides potato chips having substantially the same flavor,color, crispness and a slightly greasy appearance similar toconventional deep-fried potato chips, without the need for deep-frying,but does so without the addition or deletion of any food content to thenatural potato. The result is a completely natural potato chip which isvery low in fat.

SUMMARY OF THE INVENTION

Briefly, the present invention is directed to a process for preparingpotato chips having substantially the same flavor, color, crispness anda slightly greasy appearance similar to deep-fried potato chips but inwhich no fat content is added to the natural potato and none of thenatural foodstuffs therein are removed. The process comprises the stepsof washing the potatoes to remove foreign matter from the skin thereof,cutting the potato into thin slices, optionally washing or blanching theslices, and heating the slices of potato in a microwave oven for aboutthree to ten minutes depending on the power and efficiency of themicrowave equipment and the quantity of slices being subjected to themicrowaves. Depending on the food contact surface used in the microwaveoven, the slices of potato can be rotated 180° at the mid-point of themicrowave heating step to prevent the potato slices from adhering to thecontact surface. After heating, the chips are removed from the microwaveoven and are ready for consumption. If desired, salt can be added priorto or after the microwave heating. Other natural seasonings can also beadded to the chips but preferably after microwave heating to avoidburning the seasonings.

To reduce the cooking time in the microwave oven and the costsassociated therewith, the potato slices are preferably preheated priorto microwaving. While baking and steaming have been successfullyemployed in this preheating step, it has been found that preheating withdry heat, i.e., baking, is preferred due to the reduction in themoisture content of the slices which can be achieved with dry heat.Substantially reducing the moisture level in the slices prior tomicrowaving not only reduces the microwaving time but appears to providea superior product. Such preheating should be conducted at a temperatureand for a time sufficient to remove from about 50% to 80% of themoisture from the slices prior to microwaving and preferably between 65%to 70%. By preheating the slices at a relatively high temperature andfor a relatively short period of time to obtain such a reduction in themoisture content of the slices, the subsequently microwaved chipsconsistently exhibit the same flavor, color, crispness and slightlygreasy appearance as deep-fried potato chips. If a reduced moisturecontent is desired in the chip to increase the shelf-life of theproduct, the time of the microwave heating step can be slightly extendedor, more preferably, the cooked chips can be subjected to a microwavedrying step wherein the chips are again exposed to microwave energy, butat a lower intensity. Completing the chip preparation process at a lowermicrowave power level provides more control over the final moisturelevel of the chips through variations in the time and power level of themicrowave drying step. In addition to producing low fat potato chips,the process of the present invention can also be used to produceshoestring potatoes and other tuber chips and shoestrings without theaddition of any fat and without removing any of the natural foodstuffs.

It is the principal object of the present invention to provide animproved process for preparing potato chips which have the same flavor,color, crispness and slightly greasy appearance as deep-fried potatochips but which does not add any additional fat content to the naturalpotato nor removes any of the natural foodstuffs from the potato.

It is another object of the present invention to provide an improvedprocess for preparing potato chips which obviates the need to add anyother food item or chemical to the potato during the process.

It is yet another object of the present invention to provide an improvedprocess for preparing potato chips which eliminates the need to fry thechips in oil during the process.

It is yet another object of the present invention to provide an improvedprocess for preparing shoestring potatoes which does not add anyadditional fat content to the natural potato to provide a low fatshoestring potato and which does not remove any of the naturalfoodstuffs from the potato.

These and other objects and advantages of the present invention willbecome readily apparent from the following detailed description.

DESCRIPTION OF TEE PREFERRED EMBODIMENT

In the process of the present invention, the potatoes are first washedand scrubbed in a customary manner to remove any foreign matter from theexterior skin thereof. The washed potatoes are then sliced, preferablywithout removing the skins, to a thickness of about 1/16 of an inch. Thepotato slices can then be washed or blanched as is customarily done in aconventional potato chip manufacturing process. The chips are laid on aceramic or other suitable plate, placed in a microwave oven and heatedin the microwave oven from about three to ten minutes, depending on thewattage of the microwave oven and the quantity of the slices beingcooked. In a typical microwave oven designed for home use and having apower rating of about seven hundred to one thousand watts and operatingat about 2450 Mhz, a batch of about two dozen of the cut slices areheated for about six to ten minutes at a full power setting, with abouteight minutes being the optimum heating time. In a commercial microwaveunit having a power rating within the range of about fifty to threehundred kilowatts and operating at about 915 Mhz, the heating time couldbe reduced to one minute or less, depending on the power and efficiencyof the microwave oven and number of chips being cooked.

To prevent the potato slices from adhering to the plate, the slices arepreferably turned 180° at the mid-point of the heating. If a non-stickplate surface is employed, turning of the potato slices is notnecessary. Alternatively, a support tray could be employed for stackingthe slices on and in a vertical disposition within the microwave oven toprevent the potato slices from sticking to the plate without the needfor interrupting the heating process to turn the slices. For commercialoperations, a continuous heating cycle could be employed in which thepotato slices are placed on a conveyor which runs through a microwaveheating station for mass producing the potato chips of the presentinvention. At the completion of the heating period in the microwaveoven, the chips are removed and are ready for consumption or packaging.

In certain instances, it may be desirable to reduce the time of themicrowave heating process for energy or other considerations. By heatingthe slices of potatoes prior to microwaving (referred to herein aspreheating), the time necessary for microwaving the then partiallycooked potato slices can be reduced. It has been found that preheatingthe slices in an oven such that from about 50% up to 80% of the moisturecontent of the slices is removed prior to microwaving significantlyreduces the microwaving time and the costs associated therewith andimproves the crispness and taste of the final product. Removal of about65% to 70% is actually preferred. If more than 80% of the moisture isremoved, the slices become too hard and the subsequent microwaving stepwill not produce the desired crisp and light chip. If less than 50% ofthe moisture is removed, the potential benefits resulting preheating arenot fully realized. As the amount of pre-microwave heating moisturereduction increases from the elimination of mere surface moisture(defined in U.S. Pat. No. 5,202,139 as being about a 6% moisturereduction) to the desired level of 50% to 80%, the economic benefit ofsuch moisture reduction becomes more significant until the preferredlevel of moisture reduction of about 6% to 70% is reached. At moisturereduction levels of about 20% to 25%, well below the desired range, butstill substantially in excess of the elimination of only the surfacemoisture in the chips, the economic benefits, though not fully realized,are still significant. The quality of the chips produced employing a 20%to 25% pre-microwave reduction in the chip moisture, while not as highas those made using the preferred range of pre-microwave moisturereduction, would still exceed those in which only a minimal amount ofmoisture was removed from the slices prior to microwaving. For bestresults, however, the higher range of to 80% of the chip moisture, andmost preferably 65% to 70% thereof, should be reduced during thepre-microwave heating step. The moisture reduction can be achieved in anon-commercial application by heating the slices at a temperature withinthe range of about 250 to 500 degrees Fahrenheit. For example, bakingthe chips at about 400° F. for a period of six to twelve minutes willreduce the microwave cooking time in a home microwave oven to aboutthree to seven minutes, with the optimum baking time for about twentychips being about ten minutes and the microwave cooking time being about5 minutes.

In mass production commercial applications of the present invention,preheating at higher temperatures for shorter periods of time ispreferred, both to reduce the microwaving time and to enhance thequality of the product. It has been found that by baking the slices athigh temperatures within the range of about 500° to 800° Fahrenheit forabout 30 to 120 seconds, and preferably at about 700° F. for 50 seconds,not only can the microwaving time be reduced to about 20 seconds to 5minutes, depending on the volume of slices and the microwavingapparatus, but the quality of the product is improved. It is believedthat the preheating temperature range could be extended to about 900° F.which would reduce the lower end of the preheating time range to about20 seconds. By preheating within this higher temperature range, the airpockets common to deep-fried chips begin to form during the preheatingof the raw slices and, the subsequent microwaving appears to moreconsistently provide the chips with the same light crispiness andtexture of deep-fried chips.

By way of example, potato chips having the same flavor, color, crispnessand slightly greasy appearance as deep-fried potato chips but having noadded fat content could be produced by baking 25 pounds of potato slicesof about 1/16 of an inch thick in an oven for 50 seconds at 700°Fahrenheit. The preheated chips are then directed to a microwave ovenhaving a power rating of about 120 kw and exposed to the microwaves fora period of about 115 seconds.

Similar results might also be obtained in commercial applications atlower temperatures in the range of 250° to 500° Fahrenheit by usingovens providing a heated airflow directed about the potato slices. Themovement of heated air about the slices during a pre-microwave heatingstep promotes more rapid moisture removal from the slices and thusreduces the preheating time. The more rapid air movement about theslices, the more quickly the moisture is removed. However, the use ofrapidly circulating air about the slices in the oven tends to produce achip which has a somewhat dull appearance. This can be overcome bysteaming the raw slices prior to such preheating until the slicesexhibit a slick, shiny appearance. This typically occurs in about 30 to90 seconds. The slices could also be boiled in water for a period ofabout 10 seconds to one minute in lieu of steaming but with boiling, theslick, shiny appearance, which is indicative of the completion of thisstep, is not readily apparent.

While a precise correlation between preheating times and temperaturesand microwaving power ratings and times has not been determined,increasing the temperature in the preheating step and/or providingheated air movement during the step will reduce the preheating timerequired to obtain the desired moisture reduction. Increasing themoisture reduction within the prescribed limits will reduce themicrowaving time. However, potato slices preheated to the desiredmoisture reduction level at an elevated temperature within the range ofabout 500° to 900° F., and preferably at about 700° F., will generallyprovide a superior chip to slices preheated at a lower temperature andfor a longer time to provide the same moisture reduction level. Theoverall chip processing time in commercial applications employing apreheating step could be reduced by overlapping the preheating andmicrowaving steps. In such instances, the preheating temperature wouldpreferably be reduced during the overlapping period, particularly if arelatively high preheating temperature were employed. In addition, themicrowave energy may be applied intermittently to reduce total energyconsumption.

To increase the shelf life of the chips cooked by the above-describedpreheating and microwaving steps, the cooked chips could be furtherdried by a second microwaving step. This could be accomplished with atypical home microwaving oven with a maximum power rating of onekilowatt by subjecting the cooked chips to the microwaves at a mediumpower setting for a period of about one and one half to six minutes,with about three minutes being preferred. In a commercial application,the power in the second microwave unit would be reduced by at least 50%and more typically 75% to 80% from that employed in the microwavecooking step and the chips would also be exposed to the microwaves forabout one to six minutes.

If desired, salt or other natural seasonings can be added to the potatoslices. Salt can be added prior to or after heating the chips in themicrowave oven, whereas other seasonings which are susceptible toburning should be added after the microwave heating step. If seasoningsare added to the potato slices after microwave heating, it may benecessary to add a very small amount of oil or other suitable medium tothe cooked chips or to the seasoning so that the seasoning will adhereto the cooked potato product. Such a medium could comprise a solution ofwater and gum acacia. When using such as medium, the water would have tobe evaporated by the subsequent application of heat at a temperature andfor a time which did not further cook the chips. It has been found thatan attractive flavor can be added to the chips without adding any fatand without the need for such an additional application of heat bydipping or soaking the raw slices in a vinegar and water solution,preferably employing red wine vinegar, prior to the preheating step.Other non-fat flavorings in a liquid state could be similarly applied tothe chips if desired.

Completing the process at a lower power allows for better control overthe moisture level of the final product through variations in the timeof the second microwaving step and/or by regulating the power level atwhich this final drying step is conducted. It also allows for bettercontrol over the final appearance of the chips in that the coloring ofthe chips can be more closely regulated at the lower power level to meetthe manufacturer's desires. When employing a second microwaving step ata reduced power level for improved moisture control over the process,the duration of the microwave cooking step may be slightly reduced. Themoisture control of the chips can be further enhanced by introducingheated air into the microwave oven during the second microwave step at atemperature of from about 150° to 400° Fahrenheit (preferably about 275°F.). To optimize such moisture control as well as control over desiredcolor variations, the temperature of such air should be selectivelyvariable within this range. In some instances, the additional drying ofthe chips might be achieved solely with the use of heated air withoutthe second microwaving step. Alternatively, a radio frequency dryercould be used in lieu of a second microwaving. The use of radiofrequency waves for further drying of the chips may be advantageous whenit is desired to remove moisture from the chips with minimal heating ofthe chips so as to avoid further browning. A radio frequency dryersuitable for such purposes is marketed by Proctor Strayfield, a divisionof Proctor and Schwartz of Horsham, Pa.

An example of apparatus for commercially producing chips in accordancewith the present invention comprises a conveyor system to providecontinuous chip production, a gas-fired oven and one or two microwavingstations. The individual slices would be continuously transported on theconveyor through the oven in a spaced array so as to provide evenheating of the individual chips. The speed of the conveyor through theoven would be set relative to the oven temperature, preferably at about700° F., to provide the residence time within the oven necessary toachieve the desired moisture reduction within the slices. The conveyorcould comprise a single belt traveling linearly through the oven or, toreduce the overall length of the oven, a single belt traveling in atortuous path or a plurality of belts arranged such that the potatoslices travel back and forth within the oven as they are deposed fromone belt onto another. A conveyor belt would then transport thepreheated chips from the oven into a microwave station where the chipswould be subjected to the microwaves for a predetermined period of time,preferably at a relatively high power level of about 300 kw, althoughpower ratings within the range of from about 1 kw up to 600 kw could beemployed. The upper power limit of the microwave station has yet to beestablished. The conveyor belt moves the chips through the microwavestation at a speed selected so as to provide the necessary microwaveheating time within the station given the extent of preheating and thepower level of the microwave station. Alternatively, the conveyor beltcould transfer the chips within the microwave station in a stackeddisposition onto one or more slower moving belts after such time as thechips were sufficiently dried so as not to stick together. Through sucha multi-belt configuration, the size of the microwave station could bereduced. The chips are then conveyed through a reduced power microwavestation for further drying of the chips to the final desired moisturelevel for prolonged shelf life which is generally about 2%. To provideflexibility in the system, the speed of the conveyor belt or beltsemployed in the conveyor system would be adjustable as would be the oventemperature and power levels in the microwave stations.

In addition to potato chips, the aforesaid process can be used toproduce shoestring style potatoes. To produce shoestring potatoes, thesame process is employed except that the potatoes, after washing aresliced into elongated or curved strips of the desired configuration andlength, preferably about 1/16-1/8 in. in thickness, and heated in a homemicrowave oven for about six to twelve minutes depending on thickness ofthe strips or for as short a time as about one minute in a commercialmicrowave oven. As with the potato slices, the potato strips can also bepreheated prior to microwaving to reduce the microwave heating time. Asshoestring potatoes are generally somewhat thicker than potato chips,their preheating and microwaving times will be slightly greater than thecorresponding times for pre-heating and microwaving the slices used inthe production of potato chips. For example, by baking the strips atabout 400° Fahrenheit for about six to fourteen minutes, the microwaveheating time is reduced to about three to ten minutes in home units andto about thirty seconds to six minutes in commercial microwave unit,depending on the power and efficiency of the microwave oven and thenumber of strips being cooked. If the strips were preheated in acommercial application by baking at a temperature of about 700° F. for aperiod of about one minute, the microwaving time required to produce thedesired product would be about two and one-quarter minutes. As with thechips, the microwaved strips could be further dried by a secondmicrowaving step to increase the shelf life of the product. This couldbe accomplished by using substantially the same above-describedparameters employed with the potato chips.

Other low fat chips comprised of other tubers and vegetables such assweet potatoes, yams and beets as well as chips comprised of mixedingredients such dried potato and other tuber flakes dried vegetablesand/or grains, mixed in water, as well as tortilla chips, could beprepared utilizing the aforesaid processes. With chips employing mixedingredients such as tortilla chips, the chips would be press formed in aconventional manner, i.e., rolled to a thin sheet and cut, as opposed tosliced, and then microwave cooked, heated and microwave cooked orheated, microwave cooked, and dried using microwave heating, radiofrequency heating or convection air as previously described. In thepreparation of tortilla chips, however, the baking time is preferablyreduced to a range of about twenty seconds to two minutes while thebaking temperature range can range from about 250 to 900 degreesFahrenheit depending on the type and configuration of oven being used.In addition, if a second microwave step were employed after themicrowave cooking step to further dry and increase the shelf life of thechips, the cooked tortilla chips would be exposed to the microwaves atthe above-described reduced power settings for a period of about 45seconds to 5 minutes.

Various changes and modifications may be made in carrying out thepresent invention without departing from the spirit and scope thereof.Insofar as these changes and modifications are within the purview of theappended claims, they are to be considered as part of the presentinvention.

I claim:
 1. A method for preparing a potato product having a low fatcontent in which none of the natural foodstuffs of the potato areremoved, said method comprising the following steps: cutting a potato toproduce a plurality of potato slices; baking the slices; and microwaveheating the baked slices for a period of time sufficient to produce aproduct having substantially the same, color and crispness as deep-friedpotato chips and having no added fat content.
 2. The method of claim 1wherein said microwaving step occurs continuously.
 3. A method forpreparing a tuber chip product having a low fat content in which none ofthe natural foodstuffs of the tuber are removed, said method comprisingthe following steps: cutting a tuber to produce a plurality of tuberslices; baking the slices; and microwave heating the baked slices for aperiod of time sufficient to produce a product having substantially thesame color and crispness as deep-fried tuber chips and having no addedfat content.
 4. The method of claim 3 wherein said microwaving stepoccurs continuously.
 5. A method for preparing a potato product having alow fat content in which none of the natural foodstuffs of the potatoare removed, said method comprising the following steps: cutting apotato to produce a plurality of potato strips; baking the strips; andmicrowave heating the baked strips for a period of time sufficient toproduce a product having substantially the same color and crispness asdeep-fried shoestring potatoes and having no added fat content.
 6. Themethod of claim 5 wherein said microwaving step occurs continuously.